We present the unplanned detection of a white dwarf companion to the star HD 218261 in mid-infrared (10–16  |$\mu$| m) observations with JWST /MIRI. This star was observed as a calibrator for coronagraphic observations of the exoplanet host HR 8799. HD 218261 B has only previously been detected by Gaia , and only in visible light. We confidently detect the companion in the mid-infrared, where it is less luminous than the primary by a factor of |${\sim} 10^4$|⁠. The visible and mid-infrared photometry are consistent with a white dwarf of |$T_\text{eff}\approx 10000$|  K, |$M\approx 0.8~\mathrm{ M}_\odot$|⁠ , though observation of its optical spectrum is required to precisely constrain its physical parameters. These results demonstrate that precise mid-infrared photometry of white dwarf companions to bright stars can be obtained with MIRI, opening up new possibilities for studying white dwarfs in close binaries. [ABSTRACT FROM AUTHOR]

Copyright of Monthly Notices of the Royal Astronomical Society: Letters is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)